High-temperature corrosion (hot corrosion) is a mechanism of corrosion that takes place in gas turbines, diesel engines, furnaces or other machinery coming in contact with hot gas containing certain contaminants. The hardware of such machinery, e.g., a turbine blade, is continuously threatened by extreme hot corrosion. In such region of gas turbines or engines, subsequent coating may be applied to provide a superior hot-corrosion resistance to gas turbines.
Many factors in such coating systems, both microstructural (grain size, distribution of second phase precipitates, etc.) and compositional (chemical homogeneity, bulk content of refractory metal, Cr, Co, Al, Y, Hf, etc.), can influence hot corrosion resistance performance. Among those, chromium (Cr) content is a key contributor to hot corrosion resistance. As such, it has been common to apply a secondary coating under the high chromium cathodic arc coating to increase hot-corrosion resistance.
Nevertheless, the conventional combined coating process requires considerable additional cost and causes significant loss in coating thickness due to aggressive grit blast and spallation. As such, there is a need to provide a coating which provides High-temperature corrosion (hot corrosion) resistance without the cost and loss associated with conventional methods.